Once, when I was in college, I wrote home complaining about the food, and my mother sent me a Julia Child cookbook. In the book was a section on dealing with eggs in which she said that the sign of a really good cook is knowing eggs. And so I took an egg out. You can watch an egg – you can learn certain things just by watching it, but you don’t learn very much. To learn about eggs you have to put them in a pan and try to make something out of them. If you do this long enough you begin to understand that there are variations in eggs, and there are certain ways that they react to heat and ways that they react to oil or butter or whatever. And so by actually working with the egg and trying to make something out of it, you really come to understand eggs.
And it’s the same with the mind: unless you actually try to make something out of the mind, try to get a mental state going and keep it going, you don’t really know your own mind. You don’t know the processes of cause and effect within the mind. There has to be a factor of actual participation in the process. That way you can understand it. This all comes down to being observant and developing a skill.
Thanissaro Bhikkhu, The Path of Concentration & Mindfulness